Control head for indicators



Feb. 25, 1936. B. B. HOLMES CONTROL HEAD FOR INDICATORS Filed Nov. 4, 1932 2 Sheets-Sheet 1 attorneys Patented Feb. 25, 1936 UNITED STATES CONTROL HEAD FOR INDICATORS Bradford B. Holmes, Stonington,

Conn, assignor to Ruth V. Holmes, Stonington, Conn. Application November 4, 1932, Serial No. 641,275

11 Claims.

This invention relates to control heads for compasses and other indicating devices, and particularly to heads adapted for use with compasses The invention disclosed herein constitutes an improvement upon the structure disclosed and claimed in my copending application Serial No. 374,098, filed June 27, 1929, now Patent 1,939,775, December 19, 1933, reissued as No. 19,338, October 9, 1934; as well as that of Serial No. 412,418, filed December 7, 1929, now Patent No. 1,993,548, March 5, 1935. In these applications, disclosure was made of different types of control heads rotatably secured to a compass or other indicating instrument, but the heads were not closed at the bottom against the entry of dirt and moisture, nor could they be removed without disarrangin the contact mechanism. Furthermore, in the cases referred to, the armature of the control head was secured to the contact arm, thereby increasing its mass and inertia and preventing relative rotation between the two. Also, the diameter of the spindle was so small that a substantial armature bearing could not be provided. By enclosing the control head in a dust and moisture tight casing, and refining the structural arrangement of the contact arm lifting mechanism, accuracy of control and quickness of response have been tremendously improved.

One object of the invention is, therefore, to provide a control head which is removable at will from the compass or indicating device, so that the device may be used either with or without the head, and when the head is removed will function in the usual manner without adjustment or delay.

Another object is to produce a removable head which is completely sealed against the entrance of dust and moisture.

A further object of the invention is to produce a control head embodying a contact device of small mass and inertia, so that it will function quickly, accurately and positively, thereby insuring proper response of the parts to be controlled; and to provide self-contained damping means for this device.

Other objects will appear from the specification when read in conjunction with the accompanying drawings, in which:-

Figure 1 is atop plan view of one form of removable control head as it appears when in .position on a magnetic compass;

Fig. 2 is a vertical sectional view on line 11-11 of Fig. 1;

Fig. 3 is a detail sectional view of the contact lifting magnet structure shown in Fig. 2;

Fig. 4 is a sectional view of the contact arm;

Fig. 5 is a detail sectional view showing one manner of attaching the magnetic coupling element and contatt arm together; and

Fig. 6 is a. diagrammatic view of one form of circuit for controlling the lifting magnet.

The control attachment to which this invention relates is applicable to various form of indicating devices, but for the sake of illustration it has been shown as applied to a magnetic compass. It will be understood, however, that it may be applied to a gyroscopic compass or to other indicating instruments which are intended to control an electric contact device without the imposition of any appreciable load upon the indicator.

In the drawings, the reference character A has been used to designate generally a magnetic compass of the type adopted as standard by the U. S. Navy, while the reference character B has been used to indicate the removable control head to which this invention relates.

' The compass A comprises a body 1 weighted at its lower portion, as indicated at 8. The body l is mounted to oscillate about a geometrical point with the usual gimbals comprising the knife edge trunnions 9, which engage seats provided for them in gimbal ring II, and the knife edge trunnions 12, which engage seats provided for them in the fixed supporting ring 13.

The chamber l4 within the compass contains the usual damping liquid which is confined by the cover glass 15. This glass is sealed by a gasket I6, and it and the gasket are retained by the ring I! which is fastened in place by screws l8, as shown.

Mounted at the center of the housing I is an upstanding pin I9 which carries at its top the pivot 2| the tip of the pivot being coincident with the point about which the compass tilts. Coacting with the pivot 2| is a conical bearing formed in a screw 22. This is threaded into a sleeve which extends axially through the hollow float 23.

The purpose of the float is to sustain the compass card and the needles and thus reduce the load on the pivot 2|. There are four tubes 24 which contain the magnetic needles used to give the compass its directional characteristic. Of the four of these shown, two are longer than the other two and pass through the hollow float 23. The shorter two are substantially tangent to the sides oi. the float, all four needle tubes being in mutual parallel relation with one another. It will be understood that the tubes make tight joints brackets 25 is the annular compass card 26, bearing any desired indicia. Familiarmarkings have been sketched in Fig. 1.

The invention can be applied without modifying the compass at all, but I prefer to add to the compass one additional bar magnet which is parallel'with the tubes 24 and which is mounted on the top of the float 23 so as to be as near as possible to the cover glass l5. This magnet appears at 21. Its north seeking end is presented in the same direction as'the north seeking ends of the needles in the tubes 24, and it may be re-= garded merely as an aumliary magnet acting in concert-with the regular needles. From another point of view, it may be regarded as a means for creating a magnetic fleld attached to any indicating device, whether that indicating device be magnetic in its characteristics, or not.

The control head designated B comprises an annular casing 28, including a depending flange portion l0 adapted to flt over the'top of the compass A. The inside of this flange is of greater diameter than the top of the compass in order to facilitate attachment and removal of the head.

In the clearance provided between the vertical wall of the top of the compass and the insides! flange I0, are two spaced lugs or pads and 30, disposed approximately 120 apart.

The'rlng III also carries on one side, opposed" to the pads 20 and 30, a spring-pressed lug 40 workingin an aperture 50, and biased inwardly by a spring 60 secured at both'ends to the flange l0 and carrying centrally thereof the lug 44. The lower face of lug 40 is beveled to facilitate engagement of the head with the compass when the head is lowered into position. It will be seen that the head B-may be rotated freely with respect to the top of the compass, but that spring 60 forcing lug-40 against the compass casing will oppose slight frictional engagement to the lifting of the headfrom the compass. I

Secured to the casing 28 is a ring 25, held in place by screws 3| and including a bottom glass 32 cementedto it in water-tight relation. The

glass 32 preferably carries on its top side and at the periphery thereof, an etched azimuth circle or an azimuthcircle can'ied .by an additional ring, whereby a course may be set. As shown in the drawings, this azimuth circle is indicated at a.

In the center of the glass 32 is a ring 34 threaded interiorly to carry a disc or anvil 35 for sup-.

porting the spindle of the contact arm in: its lowered position and acting as a stop therefor. The ring 34 is spun into the glass in water-tight V relation thereto and the'dlsc 35 may beadiusted up and-down, as conditions -may require.

carried in the ring.

Above the contact ring 31 is an insulating ring j 39 engaging the bottom side of a cover glass 4|.

The space between the top of casing 28 and the top-of this glass is preferably sealed by a rubber washer 42 fitting between the glass and aflange on thecasing. The rubber ring 39 is of greater axial extent than the space in which it fits, so that when screws 3! are tightened, the ring 39 is compressed and holds the parts in water-tight rigid relation.

The cover glass 4! is perforated in the center net structure supported by a plurality of screws 41 and comprising a magnetizable shell or casing 48 open at the bottom, and containing a solenoid 49 made up of a very large number of turns of fine wire. This solenoid is carried on a central healing or guide in the form of 'a tube 5i of non-magnetic material, such as brass, from which the wires 49 are insulated by an insulating tube 52. Discs 53 of insulating material complete the separation of the wires 49 from the magnetic structure of the magnet, while the bottom end of housing 48 is closed by a magnetizable disc 54. I

The top of housing 44 is closed by a cap 55 of non-magnetic material secured thereon by screws 56 and separated from the housing proper by a sealing ring 51. cap contains a chamber-58 within which the contact arm spindle can netic sleeve 62' which extends throughout the length of the solenoid and is freely slidable within, the tube59. n

I The armature 6! also carries around its top face a washer 63. of non-magnetic material, designed to prevent armature 6i andtube 58 from coming into contact and thus preventing the residual magnetism in these elements from causing them to stick together whenthe armature is lifted by energization of the solenoid.

Fixedly mounted within the non-magnetic tube 62 are two bushings 64 and 65' of insulating non-magnetic material, such as ivory, agate or other suitable bearing jewel material, and acting as bearings for a contact arm spindle 6G. The spindle 86 is capable of shifting in the bushings 84 and 55, but its upward movement is dependent on movement of sleeve 62 and armature 6| when the solenoid 49 is energized. The top end of spindle B6 is threaded to receive a rubber nut 61 which absorbs the shock when the tube 62 rises and hits it, and at the same time makes it possible to adjust the contact arm accurately with an adjustment which does not jar loose.

The lower end of spindle 66 carries a head 68 of non-magnetic material through which the spindle passes, as shown in Fig. 5. The head 68 contains two aligned apertures. for the reception of magnetic coupling magnets 59, which are driven tightly therein in alignment with each other and disposed at right angles to the axis of contact arm H. The contact arm is preferably secured to the head by heading down, as shown in Fig. 5. This contact arm may very well be made from a light metal, such as aluminum, and

is centrally ribbed at 12 to mak it-stifl. This 75 arm carries at its extremities electric contact buttons 13 and 14 composed of electrically conducting metal having a high melting point and low vapor pressure and non-corrosive, such for example as platinum iridium. These buttons cooperate with the contacts carried by insulating ring 31.

When the solenoid 49 is energized, armature BI is drawn upwardly within the tube 5|, carrying with it tube 62, spindle 86, and contact arm H and bringing the contact buttons 13 and 14 into engagement with contacts 38* and 38, respectively, thereby limiting this upward movement. When the solenoid is deenergized, the contact arm drops by gravity until the lower pointed end of spindle 88 engages the adjustable anvil 35, and its downward movement is cushioned by the damping action of chamber 89 as the air is sucked into it through the restricted passage between tubes 62 and 59.

The configuration of contact arm 1! includes a slight upward bow, so that when it is drawn upwardly it has a slight spring and when disengaged, its resiliency facilitates quick disengagement between the buttons 13 and ll and the contacts in ring 31.

Current is supplied to the solenoid 49 through two conductors l5 and 76, which pass through an opening 11 in casing 48 and the conductors are insulated therefrom by a tube oi insulation 18, the free ends of which are split and secured to the solenoid 88 at 19. The conductors l5 and 16 pass through an extension of insulating tube 18 and thence join the conductors leading to contacts 38, all of them being carried in a flat flexible woven cable 82 which enters the head of the casing through a water-tight opening 83, sealed by cement. Secured to this head adjacent the cable 82 is a flat curved support 84 which prevents the conductors within cable 82 from being broken by their bending abruptly over the edge or the casing, and this support as cable are held in place by a clamp 50. This fiat cable solves the diflicult problem of bringing wires to the head without restricting the movement of the compass in its gimbals. Inasmuch as the cable 82 imposes a weight upon the compass'head where it enters, and this weight unbalances the compass, this effect is overcome by mounting on the head diametrically across from the cable a load counterbalancing weight 85, suitably secured thereto as .by screws 86.

The circuits involved in this apparatus will be clear from an examination of Fig. 6, wherein the conductors l5 and 16 are indicated as being connected to the solenoid l8 and controlled by a circuit controlling disc 81. As illustrated, the circuit controller 81 comprises a rotatable disc of insulation containing conducting segments 8| connected together by a wire 82. Two brushes 88 contact with the periphery of the disc and in the position shown complete the circuit of conductor 18. When the disc rotates to disconnect the brushes from the segments, this circuit is open.

Connected to the contacts 38 are leads l8. Conductor 16 leading from one terminal of the source of current is connected to segment 88 by wire 80. The wires 18 connected to contacts 88 are also connected to the other terminal of the source by operating circuits, not shown. Inasmuch as the circuits controlled by contacts 38 and 88 in insulating ring 31 are not essential to an understanding of this invention, it will sumce to state that when conductors 18 well as the and 18 are connected to a suitable source 01' current by closing switch 88 and rotating circuit controller 81, the solenoid 49 will be energized to lift the contact arm, while upon further rotation 01' circuit controller 81, this circult will be broken.

When the control head 13 is placed in position on the compass, as shown in Figs. 1 and 2, the magnets 88 swing into the magnetic stream of the compass, thereby making them parallel to the needles and tubes 24. Inasmuch asthe needles or the compass assume a north and south position, the contact arm II will be in an east and west position, and as shown will be in proximity to the contacts 88 and 88-.

Each time that conductors 1'5 and 16 are energized, the solenoid 48 is energized and lifts the contact arm 'H to complete a circuit through the contacts, with which the arm 1! is in alignment. When this circuit is broken, or the circuit established in any conductor 18, the contact arm will drop and will realign itself with the compass, due to the magnetic attraction between coupling magnets 88 and the magnet 21 carried by the compass bowl.

Chamber 89 acts as an air damping chamber from which the air is iorced out along the clearance between tubes 82 and 58. This does not appreciably slow up the lift of the armature due to the strong magnetic pull, but on the drop of the armature air must be sucked back into the chamber and a decided slowing up of the drop occurs so that the spindle and pivot 88 is eased back onto the anvil 85 without bounce. The spindle 88 is freely movable inside of armature tube 6! so that the weight of the armature is not carried by the contact arm. This materially reduces the inertia of the contact arm and causes it to operate quickly and positively.

The working parts of the circuit controlling device are completely sealed between two sheets of glass, sothat they are fully protected against dust and molstureand the slight heat developed in the solenoid 49 is sufllcient to counteract the collection of moisture within the contact arm chamber. The azimuth circle carried by bottom glass 32 enables the operator to set a course by turning the head until the desired course appears above the lubber line of the compass. When this course has been established, the circult controller will operate to maintain it.

It will be clear that the control head has no mechanical connection with the movable indieating member and may, therefore, be removed without disturbing the operation or the indicating member. The indicator may be used either with or without the control head and the change from one use to the other may be made quickly without the use of tools and without any adjustment of the erly orientate the control head when it is applied.

Although the control head has been illustrated and described as applied to a magnetic compass, it is obvious that it is capable of use in connection with any indicating device of this general character, where a rotatable indicating member is capable oi. having a magnetic coupling element attached to it. Accordingly, no limitations Parts other than to propare implied other than those expressly stated in the claims.

What is claimed is:

1. A removable control head for indicating instruments. comprising a pair of spaced parallel 4 transparent plates mounted in watertight relation to an enclosing ring; a plurality of electric contacts mounted concentrically within the space between said plates; a rotatable contact arm adapted for cooperation with said contacts; and

an electromagnet' mounted between said plates and adapted to lift said contact arm into engagement with said contacts.

2. A removable control head forindicatmq instrumen'ts,v comprising an enclosed watertight eration with said contacts; a spindle secured to said arm; an armature rotatably but non-slidably mounted on said spindle; and a magnet for lifting said armature to bring said arm into coopera tive relation with said contacts.

4. In a control head for indicating instruments, a casing; a contact ring carried by and within said casing; a contact arm mounted in said casing for rotation with respect to said con tact ring and capable of beinglifted intocontact with it; a solenoid. having a movable core; means for securing said core to said a'rm but permitting relative rotational movement between them; means for energizing the solenoid to bring the contact arm into engagement with the contact ring; and means for damping the movement of said core and arm, when the solenoid is deenei} gized and the arm disengages the ring.

5. In a control head for indicating ments, 'aeontact ring; a contact .arm' rotatably mounted with respect to said ring and capable of movement into and out of engagement-with said ring; a magnet for lifting said arm; means comprising an enclosing ring and a pair of spacedparallel glass plates secured to said ring for enclosing said contacts, said arm and said magnet; andmeans comprising a fixed pivot for said arm secured; in the bottom one of said plates,

for adjusting the lowered position of said arm with respect to said ring.

6. In a control head for indicating instruments;

a lifting magnet comprising a solenoid; a mag-' netizable core-within said solenoid, said core comprising fixed and movable portions; a non-magnetic' member separating said portions and preventing contact between said portions when the movable portion is brought toward the fixed portion by energization of the solenoid; a fixed'contact ring; a contact arm free to rotate but secured against longitudinal movement with respect to the movable portion of said core and capable of engagement with said ring; and means for energizing' said solenoid to lift said am into contact with said ring.

7. In a control head for indicating instruments,-

a casing; a contact ring carried by said casing; a

rotatable contact arm capable of movement into and out of engagement with said ring; a lifting magnet for said arm, said magnet including a movable core; a spindle fixed to said arm but arranged to move upwardly with said core when said magnet is energized; and means comprising an air dash-pot within said magnet for-damping the downward movement of the core, spindle and arm when the magnet Ede-energized.

8. In' a removable control head for indicating instruments, a casing; a contact ring carried by said casing; a contact arm cooperating with said ring; a movable core portion rotatably secured to said arm; and a lifting magnet for said movable core portion, said magnet comprising a solenoid having a fixed core portion spaced from said movable portion to form a damping chamber with said movable portion and said solenoid when the movable portion is in motion,

9. A removable control head for magnetic compasses, comprising a pair of spaced transparent plates mounted in a ring to form a protective casing; a plurality. of electric contacts mounted concentrically within the space between said plates; a rotatable contact arm adapted for cooperation with said contacts; a magnet carried by said'contact am; an electromagnet for lifting said magnet and said arm to bring said contact arm into contact with said contacts; and. means ior damping the downward movements of said arm and magnet.

I0.In a control head for indicating instru-' i at unequalspeeds respectivelytoward and-away instru from the fixed core as the solenoid is energized and 'deenergized; a contact ring in Saidcasing; a-con'tact arm carried by and rotatable in said movable core but reciprocable only in concert with said movable core; magnetic coupling means carriedby said arm in said casing; and means forenergizing said solenoid to lift said arm into contact with said ring.

' 11. In a closed control head for indicators, a

contact ring; a contact arm cooperating with said ring; a solenoid for lifting said arm; a fixed core in said solenoid; a movable core loosely mounted for reciprocatory movement toward and away from said fixed core in response to 'energization and deenergization of said solenoid; means within said solenoid cooperating with said movable core to damp the downward movementand means for energizing said solenoid to lift said contact arm into engagement with said contact ring, and then deenergizing said solenoid to per mit said arm to drop. v .IBRADFORD B. HOLBES. 

